Semiconductor structure having integrated inductor therein

ABSTRACT

A semiconductor structure includes: a substrate; a first passivation layer over the substrate; a second passivation layer over the first passivation layer; and a magnetic core in the second passivation layer, wherein the magnetic core includes a first magnetic material layer and a second magnetic material layer over the first magnetic material layer, the first magnetic material layer and the second magnetic material layer are separated by a high resistance isolation layer, and the high resistance isolation layer has a resistivity greater than about 1.3 ohm-cm.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 16/744,793,filed on Jan. 16, 2020, which is a continuation of application Ser. No.16/205,065, filed on Nov. 29, 2018, which is a continuation ofapplication Ser. No. 15/707,240, filed on Sep. 18, 2017. All of theabove-referenced applications are hereby incorporated herein byreference in their entirety.

BACKGROUND

Generally, an inductor is a passive electrical component that can storeenergy in a magnetic field created by an electric current passingthrough it. An inductor may be constructed as a coil of conductivematerial wrapped around a core of dielectric or magnetic material. Oneparameter of an inductor that may be measured is the inductor's abilityto store magnetic energy, also known as the inductor's inductance.Another parameter that may be measured is the inductor's Quality (Q)factor. The Q factor of an inductor is a measure of the inductor'sefficiency and may be calculated as the ratio of the inductor'sinductive reactance to the inductor's resistance at a given frequency.

Traditionally, inductors are used as discrete components which areplaced on a substrate such as a printed circuit board (PCB) andconnected to other parts of the system, such as an integrated circuit(IC) chip, via contact pads and conductive traces. Discrete inductorsare bulky, require larger footprints on the PCB, and consume lots ofpower. Due to the continued miniaturization of electric devices, it isdesirable to integrate inductors into IC chips. Therefore, there is aneed for manufacturing integrated inductors that provide the benefit ofsize, cost and power reduction without sacrificing the electricalperformance.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. Specifically, dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 illustrates a cross-sectional view of a semiconductor devicehaving an integrated inductor formed in passivation layers during theBack-End-Of-Line (BEOL) processing of semiconductor manufacturingprocess in accordance with an embodiment of the present disclosure;

FIG. 2A to FIG. 2E illustrate cross-sectional views of the magnetic corein accordance with various embodiments of the present disclosure;

FIG. 3 to FIG. 13 illustrate cross-sectional views of the semiconductordevice at various stages of fabrication according to embodiments of thepresent disclosure; and

FIG. 14 is a diagram illustrating Eddy currents energy losses of anintegrated inductor with respect to different materials of isolationisolation layer according to various embodiments of the presentdisclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement or feature as illustrated in the figures. The spatially relativeterms are intended to encompass different orientations of the device inuse or operation in addition to the orientation depicted in the figures.The apparatus may be otherwise oriented (rotated 90 degrees or at otherorientations) and the spatially relative descriptors used herein maylikewise be interpreted accordingly.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the disclosure are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard deviation found in therespective testing measurements. Also, as used herein, the term “about”generally means within 10%, 5%, 1%, or 0.5% of a given value or range.Alternatively, the term “about” means within an acceptable standarderror of the mean when considered by one of ordinary skill in the art.Other than in the operating or working examples, or unless otherwiseexpressly specified, all of the numerical ranges, amounts, values andpercentages such as those for quantities of materials, durations oftimes, temperatures, operating conditions, ratios of amounts, and thelikes thereof disclosed herein should be understood as modified in allinstances by the term “about.” Accordingly, unless indicated to thecontrary, the numerical parameters set forth in the present disclosureand attached claims are approximations that can vary as desired. At thevery least, each numerical parameter should at least be construed inlight of the number of reported significant digits and by applyingordinary rounding techniques. Ranges can be expressed herein as from oneendpoint to another endpoint or between two endpoints. All rangesdisclosed herein are inclusive of the endpoints, unless specifiedotherwise.

The embodiments will be described with respect to embodiments in aspecific context, namely an integrated inductor with a magnetic core.The embodiments may also be applied, however, to other integratedcomponents.

FIG. 1 illustrates a cross-sectional view of a semiconductor device 100having an integrated inductor formed in passivation layers during theBack-End-Of-Line (BEOL) processing of semiconductor manufacturingprocess in accordance with various embodiments of the presentdisclosure. As shown in FIG. 1 , an integrated inductor 168 includes aplurality of coils or windings that are concatenated and formed around amagnetic core 142. The magnetic core 142 has an upper surface A and alower surface A′. The surfaces A and A′ are parallel to a substrate 101.Each of the plurality of coils may include an upper portion 162(hereafter upper coil segment 162) and a lower portion 132 (hereafterlower coil segment 132). In some embodiments, the lower coil segment 132is formed in a passivation layer 130 below the magnetic core 142, andthe upper coil segment 162 is formed in another passivation layer 160above the magnetic core 142, and vias 152 connect the upper coil segment162 with the lower coil segment 132.

The integrated inductor 168 may connect to conductive traces andconductive pads, which may further connect to other conductive featuresof the semiconductor device 100 to perform specific functions. Althoughnot shown in FIG. 1 , the integrated inductor may be connected through,e.g., vias to other conductive features formed in various layers of thesemiconductor device 100, in some embodiments.

The integrated inductor 168, which includes the lower coil segment 132,the vias 152, the upper coil segment 162 and the magnetic core 142, isformed in a plurality of passivation layers over semiconductor substrate101. Note that depending on the specific design for the upper coilsegment 162 and the lower coil segment 132, the upper coil segment 162or the lower coil segment 132 may not be visible in a cross-sectionalview, in some embodiments. In other embodiments, at least a portion ofthe upper coil segment 162 or/and at least a portion of the lower coilsegment 132 may not be visible in a cross-sectional view. To simplifyillustration, both the upper coils segments 162 and the lower coilsegment 132 are shown as visible in all cross-sectional views in thepresent disclosure without intent to limit. One of ordinary skill in theart will appreciate that the embodiments illustrated in the presentdisclosure can be easily applied to various designs for the upper coilssegments 162 and the lower coil segment 132 without departing from thespirit and scope of the present disclosure.

The semiconductor substrate 101 may include bulk silicon, doped orundoped, or an active layer of a silicon-on-insulator (SOI) substrate.Generally, an SOI substrate includes a layer of a semiconductor materialsuch as silicon, germanium, silicon germanium, SOI, silicon germanium oninsulator (SGOI), or combinations thereof. Other substrates that may beused include multi-layered substrates, gradient substrates, or hybridorientation substrates.

The semiconductor substrate 101 may include active devices (not shown inFIG. 1 for conciseness). As one of ordinary skill in the art willrecognize, a wide variety of active devices such as transistors,capacitors, resistors, combinations of these, and the like may be usedto generate the desired structural and functional requirements of thedesign for the semiconductor device 100. The active devices may beformed using any suitable methods.

The semiconductor substrate 101 may also include metallization layers(also not shown in FIG. 1 for conciseness). The metallization layers maybe formed over the active devices and are designed to connect thevarious active devices to form functional circuitry. The metallizationlayers (not shown) may be formed of alternating layers of dielectric(e.g., low-k dielectric material) and conductive material (e.g., copper)and may be formed through any suitable process (such as deposition,damascene, dual damascene, etc.).

As illustrated in FIG. 1 , passivation layers (e.g., a first passivationlayer 110, a second passivation layer 120, the third passivation layer130, a fourth passivation layer 140 and the fifth passivation layer 160)are formed consecutively over the substrate 101, in some embodiments.The first passivation layer 110 may be disposed over the substrate 101,and post-passivation interconnect (PPI) 112 may be formed in the firstpassivation layer 110. The PPI may be connected to metal layers in thesubstrate 101 or other layers of the semiconductor device 100 by vias(not shown), in some embodiments. The PPI may be connected to the lowercoil segment 132 formed in the third passivation layer 130 by the vias122, which are formed in the second passivation layer 120, in someembodiments. The magnetic core 142 is formed in the fourth passivationlayer 140 and is surrounded by and insulated from the lower coil segment132, the upper coil segment 162, and the vias 152. The magnetic core 142has a trapezoidal cross-section. However, this is not a limitation ofthe present disclosure.

A lower surface A′ of the magnetic core 142 overlies the thirdpassivation layer 130. A fifth passivation layer 160 is formed over thefourth passivation layer 140 and the magnetic core 142. The upper coilsegment 162 is formed in the fifth passivation layer 160. The vias 152extend through the fourth passivation layer 140 to connect the uppercoil segment 162 with the lower coil segment 132. Solder balls 172 maybe formed on the fifth passivation layer 160 for external connections.

The embodiment in FIG. 1 shows five passivation layers, however, one ofordinary skill in the art will appreciate that more or less than fivepassivation layers may be formed without departing from the spirit andscope of the present disclosure. For example, there may be morepassivation layers over the upper coil segment 162, and there could bemore or less passivation layers under lower coil segment 132 than thoseillustrated in FIG. 1 . In addition, other features such as contactpads, conductive traces, and external connectors may be formed in/on thesemiconductor device 100, but are not shown in FIG. 1 for conciseness.

FIG. 2A to FIG. 2E illustrate cross-sectional views of the magnetic core142 in accordance with various embodiments of the present disclosure.Throughout the various views and illustrative embodiments, likereference numbers are used to designate like elements. In FIG. 2A, afirst type of the magnetic core 142 is disclosed. The magnetic core 142is a two-layer magnetic core including magnetic material layers 203_1and 203_2 which are separated by a high resistance isolation layer205_1. By way of example, without intent of limiting, the magnetic layermay include Co_(x)Zr_(y)Ta_(z) (CZT), where x, y, and z represents theatomic percentage of cobalt (Co), zirconium (Zr), and tantalum (Ta),respectively. In some embodiments, x is in a range from about 0.85 toabout 0.95, y is in a range from about 0.025 to about 0.075, and z is ina range from about 0.025 to about 0.075. In accordance with someembodiments, the magnetic core 142 has a thickness of about 1 to 100 um,and the magnetic material layers 203_1 and 203_2 each has a thickness ofabout 0.5 to 50 um.

A purpose of the high resistance isolation layer 2051 is to mitigateelectrical current circulation in the planar magnetic coreperpendicularly to the upper surface A and the lower surface A′. Suchperpendicular currents are known in the art as Eddy currents, and theywould lead to energy losses for the integrated inductor 168. In theexemplary embodiment, Eddy currents in the integrated inductor 168 maybecome more significant due to a target operation frequency rangegreater than about 80 MHz. The high resistance isolation layer 205_1having a resistivity greater than about 1.3 ohm-cm is capable ofefficiently confining the induced eddy current to each individual layer.For example, the high resistance isolation layer 2051 may include SiO₂,Si₃N₄, AlN, Al₂O₃. In accordance with some embodiments, the highresistance isolation layer 205_1 has a thickness of about 20 to 1000angstroms.

Metal layers 201_1 and 201_2 abutting bottoms of the magnetic materiallayers 203_1 and 203_2 respectively may act as a barrier to preventoxygen from diffusing into the magnetic material layers 203_1 and 203_2,thus preventing magnetic property loss of the magnetic core 142. In theexemplary embodiment, the metal layers 201_1 and 2012 may includetantalum (Ta), titanium (Ti), or the like for its good temperaturestability, which helps to prolong device lifetime. One skilled in theart will appreciate that other material having similar desirableproperties as Ta may alternatively be used. In accordance with someembodiments, the Metal layers 201_1 and 201_2 each has a thickness ofabout 10 to 500 angstroms.

In some embodiments, the first type of the magnetic core 142 may includemore than two magnetic material layers and each two adjacent magneticmaterial layers therein are separated by one high resistance isolationlayer (the same or similar to the high resistance isolation layer 205_1)and one metal layer (the same or similar to the metal layer 201_1 and201_2).

In FIG. 2B, a second type of the magnetic core 142 is disclosed.Comparing with the first type of FIG. 2A, the magnetic core 142 of thesecond type further includes a low resistance isolation layer 204_2having a resistivity less than that of the high resistance isolationlayer 2051. In other words, the low resistance isolation layer 204_2 hasa resistivity less than about 1.3 ohm-cm. The low resistance isolationlayer 204_2 is disposed abutting a top surface of the magnetic materiallayer 203_2 and includes a material different from the high resistanceisolation layer 205_1. In the exemplary embodiment, the low resistanceisolation layer 204_2 may include oxide of the magnetic material layer203_2, i.e., oxide of CZT (OCZT). In accordance with some embodiments,the low resistance isolation layer 204_2 has a thickness substantiallythe same or similar to the high resistance isolation layer 2051. In someembodiments, the second type of the magnetic core 142 may include morethan two magnetic material layers and each two adjacent magneticmaterial layers therein are separated by one high resistance isolationlayer (the same or similar to the high resistance isolation layer 205_1)and one metal layer (the same or similar to the metal layer 201_1 and201_2), and further with the low resistance isolation layer 204_2 at thetop of the magnetic core 142.

In FIG. 2C, a third type of the magnetic core 142 is disclosed.Comparing with the first type of FIG. 2A, the magnetic core 142 of thethird type further includes one more high resistance isolation layer205_2 having a resistivity the same with the high resistance isolationlayer 205_1. In other words, the high resistance isolation layer 205_2has a resistivity greater than about 1.3 ohm-cm. The high resistanceisolation layer 205_2 is disposed abutting the top surface of themagnetic material layer 203_2 and includes a material substantially thesame with the high resistance isolation layer 205_1. The high resistanceisolation layer 205_2 may be comprised of a material the same or similarto the high resistance isolation layer 205_1. In accordance with someembodiments, the high resistance isolation layer 205_2 has a thicknesssubstantially the same or similar to the high resistance isolation layer2051. In some embodiments, the third type of the magnetic core 142 mayinclude more than two magnetic material layers and each two adjacentmagnetic material layers therein are separated by one high resistanceisolation layer (the same or similar to the high resistance isolationlayer 205_1) and one metal layer (the same or similar to the metal layer201_1 and 201_2), and further with the high resistance isolation layer205_2 at the top of the magnetic core 142.

In FIG. 2D, a fourth type of the magnetic core 142 is disclosed.Comparing with the first type of FIG. 2A, the magnetic core 142 of thefourth type further includes a low resistance isolation layer 204_1having a resistivity less than that of the high resistance isolationlayer 2051. In other words, the low resistance isolation layer 204_1 hasa resistivity less than about 1.3 ohm-cm. The low resistance isolationlayer 204_1 may be comprised of a material the same or similar to thelow resistance isolation layer 204_2 of the second type of the magneticcore 142 shown in FIG. 2B.

The low resistance isolation layer 2041 is disposed between a topsurface of the magnetic material layer 203_1 and a bottom surface of themetal layer 201_2. Therefore the low resistance isolation layer 204_1and the high resistance isolation layer 205_1 collectively form acomposite isolation layer. A total thickness of the composite isolationlayer including the low resistance isolation layer 204_1 and the highresistance isolation layer 205_1 may be greater than the high resistanceisolation layer 205_1 of the first type of the magnetic core 142.However, this is not a limitation of the present disclosure. In someembodiments, a total thickness of the composite isolation layerincluding the low resistance isolation layer 204_1 and the highresistance isolation layer 205_1 may be substantially the same with thehigh resistance isolation layer 205_1 of the first type of the magneticcore 142.

In FIG. 2E, a fifth type of the magnetic core 142 is disclosed.Comparing with the first type of FIG. 2A, the magnetic core 142 of thefifth type is a four-layer magnetic core, including four magneticmaterial layers 203_1, 203_2, 203_3 and 203_4 separated by isolationlayers 204_1, 204_2 and 204_3 and metal layers 201_2, 201_3 and 201_4.The isolation layer 205_2 disposed around mid-height of the magneticcore 142 is high resistance, and except the isolation layer 205_2, otherisolation layers 204_1 and 204_3 are low resistance isolation layers.The low resistance isolation layers 204_1 and 204_3 may be comprised ofa material the same or similar to the low resistance isolation layer204_2 of the second type of the magnetic core 142 shown in FIG. 2B andthe low resistance isolation layer 204_1 of the fourth type of themagnetic core 142 shown in FIG. 2D. The high resistance isolation layer205_2 may be comprised of a material the same or similar to the highresistance isolation layer 205_1 of the first type of the magnetic core142 shown in FIG. 2A.

FIG. 3 to FIG. 13 illustrate cross-sectional views of the semiconductordevice 100 at various stages of fabrication according to embodiments ofthe present disclosure. As illustrated in FIG. 3 , the first passivationlayer 110 may be formed on the semiconductor substrate 101. The firstpassivation layer 112 may be made of polymers, such as polybenzoxazole(PBO), polyimide, or benzocyclobutene, in some embodiments, or silicondioxide, silicon nitride, silicon oxynitride, tantalum pentoxide, oraluminum oxide, in some other embodiments. The first passivation layer112 may be formed through a process such as chemical vapor deposition(CVD), although any suitable process may be utilized. The firstpassivation layer 112 may have a thickness between about 0.5 μm andabout 5 μm, however, other ranges of thickness are also possible,depending on the designs and requirements of the semiconductor device100.

The post-passivation interconnect (PPI) 112 may be formed over thesemiconductor substrate 101 and within the first passivation layer 110to provide an electrical connection between the integrated inductor 168and other circuits of the semiconductor device 100, in some embodiments.For example, the PPI 112 may be connected to metal layers (not shown) inthe substrate 101. The PPI 112 may be comprised of copper, but othermaterials, such as aluminum, may alternatively be used. An openingthrough the first passivation layer 112 may be made in the desiredlocation of PPI 112 through a suitable process, such as a suitablephotolithographic masking and etching. For example, a photoresist (notshown) may be formed on the first passivation layer 110 and may then bepatterned in order to provide an opening in the first passivation layer110. The patterning may be performed by exposing the photoresist to aradiation such as light in order to activate photoactive chemicals thatmay make up one component of the photoresist. A positive developer or anegative developer may then be used to remove either the exposed orunexposed photoresist depending on whether positive or negativephotoresist is used.

Once the photoresist has been developed and patterned, PPI 112 may beconstructed by using the photoresist as a mask to form the opening intoor through the first passivation layer 110 using, e.g., an etchingprocess. The conductive material may then be formed into the openinginto or through the first passivation layer 110, e.g., by first applyinga seed layer (not shown) into and along the sidewalls of the opening.The seed layer may then be utilized in an electroplating process inorder to plate the conductive material into the opening into or throughthe first passivation layer 110, thereby forming the first interconnect112. However, while the material and methods discussed are suitable toform the conductive material, these materials are merely exemplary. Anyother suitable materials, such as tungsten, and any other suitableprocesses of formation, such as CVD or physical vapor deposition (PVD),may alternatively be used to form the PPI 112.

A second passivation layer 120 may be formed over the first passivationlayer 110, as illustrated in FIG. 4 . In some embodiments, the secondpassivation layer 120 may be comprised of the same material as the firstpassivation layer 110. Alternatively, the second passivation layer 120may include other suitable dielectric materials different from thematerials in the first passivation layer 110. Deposition process such asCVD, PVD, combinations thereof, or any other suitable processes offormation, can be used to form the second passivation layer 120. Thesecond passivation layer 120 may have a thickness between about 0.5 μmand about 5 μm, however, other ranges of thickness are also possible,depending on the designs and requirements of the semiconductor device100.

Vias 122 may be formed in the second passivation layer 120 to provide aconductive path between the PPI 112 in the first passivation layer 110and the integrated inductor 168 formed in subsequent processing. Thevias 122 may include copper, but other materials, such as aluminum ortungsten, may alternatively be used. The vias 122 may be formed, e.g.,by forming openings for the vias 122 through the second passivationlayer 120 using, e.g., a suitable photolithographic mask and etchingprocess. After the openings for vias 122 have been formed, vias 112 maybe formed using a seed layer (not shown) and a plating process, such aselectrochemical plating, although other processes of formation, such assputtering, evaporation, or plasma-enhanced CVD (PECVD) process, mayalternatively be used depending upon the desired materials. Once theopenings for vias 112 have been filled with conductive material, anyexcess conductive material outside of the openings for the vias 112 maybe removed, and the vias 112 and the second passivation layer 120 may beplanarized using, for example, a chemical mechanical polishing (CMP)process.

As illustrated in FIG. 5 , the lower coil segment 132 is formed over thesecond passivation layer 120. In accordance with some embodiments, thelower coil segment 132 may include copper. In one embodiment, the lowercoil segment 132 has a thickness in a range between about 5 um and about20 um. The above thickness range is merely an example, the dimensions ofthe integrated inductor 168 (e.g., the lower coil segment 132, the uppercoil segment 162, the vias 152 and the magnetic core 142) are determinedby various factors such as the functional requirements for theintegrated inductor 168 and process technologies, thus other dimensionsfor the integrated inductor 168 are possible and are fully intended tobe included within the scope of the current disclosure.

Next, a third passivation layer 130 may be formed over the secondpassivation layer 120 and the lower coil segment 132. The thirdpassivation layer 130 may be comprised of the same material as the firstpassivation layer 110 and may be formed by CVD, PVD, or any othersuitable processes of formation, in some embodiments. Alternatively, thethird passivation layer 130 may include other suitable materialsdifferent from the dielectric materials in the first passivation layer110. The thickness of the third passivation layer 130 may be larger thanthe thickness of the lower coil segment 132 so that the lower coilsegment 132 is encapsulated in the third passivation layer 130. Thethird passivation layer 112 may have a thickness between about 5 μm andabout 20 μm, however, other ranges of thickness are also possible,depending on the designs and requirements of the semiconductor device100.

Referring next to FIG. 6 , an etching process is performed to remove anupper portion of the third passivation layer 130 to expose an uppersurface of the lower coil segment 132, in some embodiments. As a resultof the etching process, openings C extend into the third passivationlayer 130. The etching process is controlled to stop when reaching thelower coil segment 132. Sidewalls of the openings C may be sloped.However, in some embodiments of the present disclosure, the openings Cmay have straight sidewalls.

Next, FIG. 7 to FIG. 11 illustrate the formation of the first type ofthe magnetic core 142 according to an embodiment of the presentdisclosure. In FIG. 7 , the metal layer 201_1 is blanket deposited overthe third passivation layer 130 and the lower coil segment 132. Themetal layer 201_1 may be made of one or more suitable materials such astantalum (Ta), titanium (Ti), or the like. A thickness of the metallayer 201_1 may be about 50 angstroms to about 300 angstroms, however,other ranges of thickness are also possible, depending on the designsand requirements of the semiconductor device 100. In FIG. 8 , themagnetic material layer 203_1 is deposited over the metal layer 201_1 bya PVD, CVD, PE-CVD, combinations thereof, or any other suitabledeposition process. In accordance with an embodiment, without intent oflimiting, the magnetic material layer 203_1 is conformally depositedover the metal layer 201_1. In accordance with some embodiments, themagnetic material layer 203_1 includes Co_(x)Zr_(y)Ta_(z) (CZT), wherex, y, and z represents the atomic percentage of cobalt (Co), zirconium(Zr), and tantalum (Ta), respectively. In some embodiments, x is in arange from about 0.85 to about 0.95, y is in a range from about 0.025 toabout 0.075, and z is in a range from about 0.025 to about 0.075. Inaccordance with some embodiments, the magnetic material layer 203_1 hasa thickness of about 5 um.

In FIG. 9 , the high resistance isolation layer 205_1 is deposited overthe magnetic material layer 203_1 through any suitable depositionprocess known in the art. In accordance with some embodiments, the highresistance isolation layer 205_1 includes SiO₂, Si₃N₄, AlN, Al₂O₃. Inaccordance with some embodiments, the high resistance isolation layer205_1 has a thickness of about 20 to 1000 angstroms. Next, the metallayer 201_2 and the magnetic material layer 203_2 are sequentiallydeposited in a way the same or similar to the deposition of the themetal layer 201_1 and the magnetic material layer 203_1 as shown in FIG.10 .

In FIG. 11 , a portion of the stacked layers including 201_1, 203_1,205_1, 201_2 and 2032 may be removed through a wet etch. The remainingstacked layers forms the magnetic core 142. A wet etching agent for thewet etch may include a HF solution, a HNO₃ solution, a CH₃COOH solution,combinations thereof, or other suitable solution. Next, as illustratedin FIG. 12 , a fourth passivation layer 140 is formed over the magneticcore 142 and the third passivation layer 130. The fourth passivationlayer 140 may be comprised of the same material as the first passivationlayer 110 and may be formed by CVD, PVD, or any other suitable processesof formation, in some embodiments. Alternatively, the fourth passivationlayer 140 may include other suitable materials different from thedielectric materials in the first passivation layer 110. The thirdpassivation layer 112 may have a thickness between about 5 μm and about10 μm, however, other ranges of thickness are also possible, dependingon the designs and requirements of the semiconductor device 100.

After the fourth passivation layer 140 is formed, the vias 152 may beformed, e.g., by forming openings for the vias 152 through the fourthpassivation layer 140 using, e.g., a lithography and etching process.The vias 152 may be formed adjacent to opposing sidewalls of themagnetic core 142. After the openings for vias 152 have been formed, thevias 152 may be formed using a seed layer (not shown) and a platingprocess, such as electrochemical plating, although other processes offormation, such as sputtering, evaporation, or PECVD process, mayalternatively be used depending upon the desired materials. Once theopenings for vias 152 have been filled with conductive material such ascopper, any excess conductive material outside of the openings for vias152 may be removed, and the vias 152 and the fourth passivation layer140 may be planarized using, for example, a CMP process.

Next, referring to FIG. 13 , the upper coil segment 162 is formed overthe fourth passivation layer 140. In some embodiments, the upper coilsegment 162 is made of copper. In one embodiment, the upper coil segment162 has a thickness in a range between about 10 um and about 15 um, suchas about 12 um. Other dimensions are possible and may depend on, forexample, the functional requirements for the integrated inductors 168and process technologies.

Next, a fifth passivation layer 160 may be formed over the fourthpassivation layer 140 and the upper coil segment 162. The fifthpassivation layer 160 may be comprised of the same material as the firstpassivation layer 110 and may be formed by CVD, PVD, or any othersuitable processes of formation, in some embodiments. Alternatively, thefifth passivation layer 160 may include other suitable materialsdifferent from the dielectric materials in the first passivation layer110. The thickness of the fifth passivation layer 160 may be larger thanthe thickness of the upper coil segment 162 so that upper coil segment162 is encapsulated in the sixth passivation layer 160 and protectedfrom outside environment. In some embodiments, one or more passivationlayers may be formed over the fifth passivation layer 160. Referringback to FIG. 1 , conductive terminals such as solder balls 172 can beformed over the fifth passivation layer 160 in order to make externalconnection to a voltage source.

FIG. 14 is a diagram illustrating Eddy currents energy losses of anintegrated inductor with respect to different materials of isolationisolation layer according to various embodiments of the presentdisclosure. The integrated inductor in the embodiment has a nine-layermagnetic core and operates at 80 MHz. As can be seen from FIG. 14 , theEddy currents energy losses reduce when the resistance of the isolationlayer increases. The Eddy currents energy losses gradually saturateswhen the resistance of the isolation layer approaches up to about 1.3ohm-cm. As such, SiO₂, Si₃N₄, AlN, Al₂O₃ are more efficiently tomitigate the Eddy currents energy losses compared to OCZT.

Some embodiments of the present disclosure provide a semiconductorstructure. The semiconductor structure includes: a substrate; a firstpassivation layer over the substrate; a second passivation layer overthe first passivation layer; and a magnetic core in the secondpassivation layer; wherein the magnetic core includes a first magneticmaterial layer and a second magnetic material layer over the firstmagnetic material layer, the first magnetic material layer and thesecond magnetic material layer are separated by a high resistanceisolation layer, and the high resistance isolation layer has aresistivity greater than about 1.3 ohm-cm.

Some embodiments of the present disclosure provide a semiconductorstructure. The semiconductor structure includes: a first passivationlayer; a second passivation layer over the first passivation layer; athird passivation layer over the second passivation; a lower coilsegment in the first passivation layer; an upper coil segment in thethird passivation layer; and a magnetic core in the second passivationlayer and insulated from the lower coil segment and the upper coilsegment; wherein the magnetic core includes a first magnetic materiallayer and a second magnetic material layer over the first magneticmaterial layer, the first magnetic material layer and the secondmagnetic material layer are separated by a composite isolation layerincluding a high resistance isolation layer and a low resistanceisolation layer, and the high resistance isolation layer has aresistivity greater than that of the low resistance isolation layer.

Some embodiments of the present disclosure provide a semiconductorstructure. The semiconductor structure includes: a first passivationlayer; a second passivation layer over the first passivation layer; athird passivation layer over the second passivation; a lower coilsegment in the first passivation layer; an upper coil segment in thethird passivation layer; and a magnetic core in the second passivationlayer and insulated from the lower coil segment and the upper coilsegment; wherein the magnetic core from bottom to top includes a firstmagnetic material layer, a second magnetic material layer, a thirdmagnetic material layer and a fourth magnetic material layer, the firstmagnetic material layer and the second magnetic material layer areseparated by a first low resistance isolation layer, the second magneticmaterial layer and the third magnetic material layer are separated by ahigh resistance isolation layer, the third magnetic material layer andthe fourth magnetic material layer are separated by a second lowresistance isolation layer, and the high resistance isolation layer hasa resistivity greater than that of the low resistance isolation layer.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother operations and structures for carrying out the same purposesand/or achieving the same advantages of the embodiments introducedherein. Those skilled in the art should also realize that suchequivalent constructions do not depart from the spirit and scope of thepresent disclosure, and that they may make various changes,substitutions, and alterations herein without departing from the spiritand scope of the present disclosure.

Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the disclosure of the present invention, processes,machines, manufacture, compositions of matter, means, methods, or steps,presently existing or later to be developed, that perform substantiallythe same function or achieve substantially the same result as thecorresponding embodiments described herein may be utilized according tothe present invention. Accordingly, the appended claims are intended toinclude within their scope such processes, machines, manufacture,compositions of matter, means, methods, or steps.

What is claimed is:
 1. A method of forming a semiconductor structure, comprising: depositing a first magnetic material layer over a substrate; depositing a high resistance isolation layer having a resistivity greater than about 1.3 ohm-cm over the first magnetic material layer; depositing a metal layer over the high resistance isolation layer before depositing a second magnetic material layer; depositing the second magnetic material layer over the high resistance isolation layer; and removing a portion of the first magnetic material layer, the high resistance isolation layer and second magnetic material layer to form a magnetic core.
 2. The method of claim 1, wherein the high resistance isolation layer includes Si₃N₄.
 3. The method of claim 1, wherein the high resistance isolation layer includes AlN.
 4. The method of claim 1, wherein the high resistance isolation layer includes Al₂O₃.
 5. The method of claim 1, wherein the metal layer includes tantalum (Ta).
 6. The method of claim 1, further comprising: forming a low resistance isolation layer having a resistivity less than about 1.3 ohm-cm on a top surface of the second magnetic material layer.
 7. The method of claim 1, further comprising: depositing another high resistance isolation layer having a resistivity greater than about 1.3 ohm-cm on a top surface of the second magnetic material layer.
 8. A method of forming a semiconductor structure, comprising: forming a lower coil segment over a semiconductor substrate; depositing a first magnetic material layer over the lower coil segment; depositing a high resistance isolation layer over the first magnetic material layer; depositing a metal layer over the high resistance isolation layer before depositing a second magnetic material layer; depositing the second magnetic material layer over the high resistance isolation layer; removing a portion of the first magnetic material layer, the high resistance isolation layer and the second magnetic material layer to form a magnetic core; and forming an upper coil segment over the magnetic core.
 9. The method of claim 8, wherein the high resistance isolation layer has a resistivity greater than about 1.3 ohm-cm.
 10. The method of claim 9, wherein the high resistance isolation layer includes Si₃N₄.
 11. The method of claim 8, further comprising: depositing a metal layer over the lower coil segment before depositing the first magnetic material layer.
 12. The method of claim 8, wherein the metal layer includes tantalum (Ta).
 13. A method of forming a semiconductor structure, comprising: forming a lower coil segment over a substrate; depositing a first magnetic material layer over the lower coil segment; depositing a first low resistance isolation layer over the first magnetic material layer; depositing a second magnetic material layer over a high resistance isolation layer; depositing the high resistance isolation layer over the second magnetic material layer; depositing a third magnetic material layer over the high resistance isolation layer; depositing a second low resistance isolation layer over the third magnetic material layer; depositing a fourth magnetic material layer over the second low resistance isolation layer; removing a portion of the first magnetic material layer, the first low resistance isolation layer, the second magnetic material layer, the high resistance isolation layer, the third magnetic material layer, the second low resistance isolation layer and the fourth magnetic material layer to form a magnetic core; and forming an upper coil segment over the magnetic core; wherein the high resistance isolation layer has a resistivity greater than that of the first low resistance isolation layer and the second low resistance isolation layer.
 14. The method of claim 13, wherein the high resistance isolation layer has a resistivity greater than about 1.3 ohm-cm.
 15. The method of claim 13, wherein the first low resistance isolation layer and the second low resistance isolation layer have a resistivity less than about 1.3 ohm-cm.
 16. The method of claim 13, wherein the high resistance isolation layer includes Al₂O₃.
 17. The method of claim 13, wherein high resistance isolation layer includes Si₃N₄.
 18. The method of claim 13, wherein high resistance isolation layer includes AlN.
 19. The method of claim 13, wherein the first low resistance isolation layer includes oxide of Co_(x)Zr_(y)Ta_(z) (CZT), wherein x, y, and z represent the atomic percentages of cobalt (Co), zirconium (Zr), and tantalum (Ta) respectively, wherein x is in a range from about 0.85 to about 0.95, y is in a range from about 0.025 to about 0.075, and z is in a range from about 0.025 to about 0.075.
 20. The method of claim 13, wherein the second low resistance isolation layer includes oxide of Co_(x)Zr_(y)Ta_(z) (CZT), wherein x, y, and z represent the atomic percentages of cobalt (Co), zirconium (Zr), and tantalum (Ta) respectively, wherein x is in a range from about 0.85 to about 0.95, y is in a range from about 0.025 to about 0.075, and z is in a range from about 0.025 to about 0.075. 